You may see the keyword ALUA frequently if you read VMware storage documents, so what’s the ALUA exactly is? How it reflects in ESXi 5.0? What’s the advantage of ALUA? I certainly have the questions, you?

First of all, ALUA is short word of “Asymmetric Logic Unit Access”, you probably already knowJ, ALUA is a SCSI standard, it’s not support by all storage arrays, but I think most large company should have the ALUA supported array. There are different articles tried to explain what ALUA is, I’m not a storage expert, I just want to give my interpretation. You may don’t agree, have question about that, please give me a comment, I’m willing to talk about that.

Generally, storage array ( Active-Active ) have two controllers (SPA, SPB), each controller have two paths (SPA0, SPA1, SPB0, SPB1), data transmits between ESX and storage array through these paths, in older ESX version, it can only use FIXED path selection policy to transmit data through a single path. Here is a potential problem, for example, you have 10 ESX hosts in a cluster mounts a LUN, one half hosts use SPA0, and the other half hosts use SPB0, it’s would cause path thrashing since first half hosts pull the LUN to storage controller SPA, and other half pulls the LUN back to storage controller SPB over and over again. Another scenario is the LUN owned by SPA but some ESX hosts transmit data through SPB for some reason.

Whatever caused the path thrashing, I guess that’s why I can saw following error in vmkernel.log:

The installer may prompt “Failed to established connection” after input SQL database information.

Reason can be vary. If your SQL account password is correct, it maybe caused by SQL password policy. The three password policy is selected by default when you create SQL account.

You could also find similiar error message in %TEMP%/vm-sso-javalib.log:

[2013-01-11 10:54:33,640]ERROR 733[main] -
com.vmware.vim.installer.core.logging.CoreLoggerImpl.error(?:?) -
Failed to established connection:
com.microsoft.sqlserver.jdbc.SQLServerException:
Login failed for user 'vCenterSSO_DBA'.
Reason: The password of the account must be changed.

We are moving virtual machine from old storage to new datastore today, there are a lot of old datastores need to be removed after migration, for saftey consideration, I move all old datastore to a folder and then do decommission process.

There are more than 60 datastores, and vSphere client not allow move in one time. Here is a PowerCLI script can help move multiple datastores to a folder.

Note: Please make sure your folder name is uniquely.

When you create datastores.txt, please make sure first line is “Name”, one datastore name in each line.
Example:Namedatastore1datastore2datastore3…

A lot of storage support hardware acceleration, it is able to offload some storage operation from ESXi 5.x host to storage filer, the feature can significantly improve performance during cloning, vMotion, coping…etc.

For block storage, we initially create VMFS5 datastore by one LUN, more LUN (extent) maybe added to the datastore when free space is low. Please be sure that all extent of VMFS5 datastore should have same ATS feature, support or not. You may see a error message “Operation failed, unable to add extent to filesystem” when you add a non-ATS extent to ATS enabled VMFS5 datastore.

How to know if lun support ATS?

You can login ESXi 5.x host via SSH and use the command to see supported feature of a lun.

esxcli storage core device vaai status get -d=device id

What is ATS?

Atomic Test and Set (ATS) is new SCSI locking method, it’s try locking per disk sector instead of reserve entire lun. More detail information in this article.

Guest OS of virtual machine can synchronize time by several way, such as NTP, VMware Tools, Windows Time Service, CMOS…etc.

VMware Tools synchronize time with ESXi host when you enable periodic time synchronization. VMware Tools time synchronization function is disabled by default, but that’s doesn’t means time synch never happens between guest OS and host. It still happens after certain operations:

When the VMware Tools daemon is started.

When resuming a VM from suspended status.

After reverting from a snapshot.

After shrinking a disk.

It can causes some problem if guest OS have different time with host, it can lead to SAP application failed due to SAP database timestamp different with guest OS.

You can completely disable the time synchronization by following step: